Electronic mail (“email”) messaging over communication networks, such as the Internet, has enabled individuals and companies to correspond over great distances at a nominal cost. In addition to routine messages, digital photographs of family members, and other noncritical data, email messages are also capable of transmitting electronic copies of business critical documents (e.g., contracts) and other sensitive information (e.g., price lists, authorization codes). Although Internet email provides great advantages in terms of cost, timeliness (rapid delivery), and flexibility (any type of digital data can be transmitted), Internet email suffers from an inherent lack of security and trustedness, which frustrates email users dealing with sensitive electronic attachments.
Email messages must typically pass through a number of different computers to get from sender to recipient, regardless of whether these computers are located within a single company, on an Intranet for example, or on Internet-attached computers belonging to a multitude of organizations. Unfortunately, any one of these intermediate computers can potentially intercept the message, keep a copy of it, and/or modify its contents. Moreover, even though some email messaging systems have limited “return receipt” capabilities, the email message carrying the receipt confirmation suffers from the same security and reliability problems as the original email message.
In order to mitigate these security issues, mathematically-based, cryptographic techniques have been applied to email messaging systems, which help ensure the privacy of email content at an added cost and complexity to email users and/or system administrators. The typical encryption methodology involves asymmetrically encrypting the sensitive electronic attachment, transferring the encrypted document to a central repository, and then authenticating the recipient to ensure that access by that entity is authorized. Unfortunately, implementation of encryption technology and maintenance of a database of encrypted documents awaiting pickup increases the cost and complexity of doing business. Accordingly, significant effort is being expended to further streamline systems that provide for a secure transfer of electronic documents at a reduced cost.